In IEEE 802.16WG, which is known as an example of a radio communication system standard, two types are specified: IEEE 802.16d concerns fixed communication (e.g. see the following Non-patent Document 1) and IEEE 802.16e concerns mobile communication (e.g. see the following Non-patent Document 2).
FIG. 22 depicts an image of the services provided by IEEE 802.16d and IEEE 802.16e. These services are based on a P-MP (Point-to-Multipoint) connection, where a plurality of terminals 101 to 103 are connected to one radio base station 100.
In this way, IEEE 802.16d or the like is based on the P-MP connection, so the service area is limited to a cover area (cell) covered by the radio base station 100, and the communication rate drops at the cell edge.
To solve this problem, in IEEE 802.16WG, a relay station to relay communication between the radio base station and radio terminals is under consideration (IEEE 802.16j).
FIG. 23 is a diagram depicting an example of a network configuration of IEEE 802.16j. In FIG. 23, the relay stations RS are disposed in order to improve the communication rates of two radio terminals MS#1 and MS#2, which are located near a cell edge of the radio base station BS.
On the other hand, in IEEE 802.16d and IEEE 802.16e, the radio terminal MS communicates with the radio base station BS according to MAP information which is sent from the radio base station BS.
For the MAP information, a radio resource which the radio terminal MS uses for communication (frequency channel and time (transmission timing): hereafter called “burst”), modulation method and encoding method of the burst, and communication target radio terminal MS, are specified. The MAP information has a DL-MAP message of a downlink direction and a UL-MAP massage of a uplink direction.
FIG. 24 depicts an example of the DL-MAP message, and FIG. 25 depicts an example of a Burst Profile DL-MAP IE (hereafter called “DL-MAP IE”) included in the DL-MAP message. One or a plurality of (n in the example of FIG. 24) DL-MAP IE(s) is or are inserted in the “DL-MAP_IE for OFDMA PHY” field of the DL-MAP message.
As FIG. 25 depicts, DL-MAP IE has a “DIUC” field and “CID” field. In the “DIUC” field, a code to indicate the modulation method and encoding method (including an encoding rate) of the burst is inserted. In the “CID” field, an identifier of a connection of a packet included in the burst is inserted, and the radio terminal MS can select the burst to be decoded by recognizing the CID.
FIG. 26 depicts an allocation example of a downlink burst by DL-MAP IE. Each burst is specified by a “Symbol Offset” or the like of the DL-MAP IE, and the radio terminal MS communicates to the radio base station BS using the allocated transmission area (frequency (ordinate) and time (abscissa)).
FIG. 27A depicts an example of the UL-MAP message, and FIG. 27B depicts an example of a Burst Profile UL-MAP IE (hereafter called “UL-MAP IE”) included in this message.
As FIG. 27B depicts, the UL-MAP IE includes “CID”, “UIUC” and “Duration” fields.
In the “CID” field, an ID to identify the radio terminal MS, which allocated the burst, is inserted, in the “UIUC” field, a code to indicate the modulation method and encoding method (including the encoding rate) of the burst is inserted, and in the “Duration” field, a band amount (number of slots) to be allocated is inserted.
FIG. 28A and FIG. 28B depict an allocation example of the uplink burst by the UL-MAP IE. As these figures depict, allocation of the uplink burst is basically defined by a number of slots. In other words, each slot is sequentially allocated in the time axis (symbol direction: abscissa) direction, shifting to the next sub-channel (ordinate) at the break point of the Uplink Zone, and the number of slots specified in the “Duration” field are allocated. Then the first slot of the next burst is allocated, continuing from the last slot of the previous burst.
As FIG. 28A and FIG. 28B depict, unlike the case of allocation of the downlink burst which is indicated by a square formed by the number of sub-channels and the number of symbols, allocation of the uplink burst is not very complete.
As FIG. 28C depicts, each burst is sequentially allocated to the uplink burst in the sequence of UL-MAP IE (“Burst Profile IE Burst #1 . . . ” in FIG. 28C).
Non-patent Document 1: IEEE Std 802.16-2004
Non-patent Document 2: IEEE Std 802.16e-2005